Citigroup Economic Surprise Index is constructed using weighted historical standard deviations of surprises (difference between actual releases and Bloomberg surveys) different macroeconomic indicators, where the weights depend on the announcement’s effect on the foreign exchange markets. With a Index over 0, its economic performance generally beats market expectations. With a Index below 0, its economic conditions are generally worse than expected. Surprise index readings climb up as economy recovers but declines fast as economy declines.